In boxing, a referee (often called the ref for short) is the person who enforces the rules of boxing withing the ring.

In the Punch-Out!! series, the referee's main job is to initiate the fight between the two boxers, and to begin counting when one of the boxers falls down. They will declare who the winner is, either by knockout, technical knockout, or a split decision.

Mario acts as the referee in Mike Tyson's Punch-Out!!, and subsequent re-releases of the game. In every other Punch-Out!! game, there is either a generic referee or no visible referee on-screen.
In the Wii game, the referee is more clearly seen than ever. He has a small mustache and is very considerate when he's deciding the winner. He also has trouble with controlling some of Mac's opponents who wants to fight immediately. In fact, Aran Ryan, Bald Bull and Super Macho Man actually attack the referee. He is also speculated to be the same referee from the arcade games.